Low drive voltage optical modulator
First Claim
1. A low drive voltage optical modulator comprising:
- a Mach-Zehnder interferometer having an input waveguide, first and second arms connected to said input waveguide splitting an input optical signal having a predetermined wavelength into a first portion and a second portion, and an output waveguide connected to said first and second arms;
a resonator having a refractive index and being operatively coupled to one of said first and said second arms across a gap; and
a voltage source connected to said resonator for providing a drive voltage thereto, wherein changes in amplitude of the drive voltage cause said resonator refractive index to change;
said changes in said resonator refractive index causing a phase-shift in the first portion of the optical signal propagating in said first arm relative to the second portion of the optical signal propagating in said second arm.
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Abstract
An optical modulator that includes a resonator near one arm of a Mach-Zehnder interferometer and that increases the optical length of that arm so as to introduce a phase-shift in an optical signal propagating in that arm when compared to an optical signal propagating in the other arm of the interferometer. The resonator also increases the electro-optic interaction between an electrical signal (i.e., the source of information in a modulated signal) and the optical devices (e.g., waveguides). A modulator constructed in accordance with the present invention is thus physically small than prior art modulators and requires a significantly reduced drive voltage to impart information on an optical signal.
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Citations
32 Claims
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1. A low drive voltage optical modulator comprising:
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a Mach-Zehnder interferometer having an input waveguide, first and second arms connected to said input waveguide splitting an input optical signal having a predetermined wavelength into a first portion and a second portion, and an output waveguide connected to said first and second arms;
a resonator having a refractive index and being operatively coupled to one of said first and said second arms across a gap; and
a voltage source connected to said resonator for providing a drive voltage thereto, wherein changes in amplitude of the drive voltage cause said resonator refractive index to change;
said changes in said resonator refractive index causing a phase-shift in the first portion of the optical signal propagating in said first arm relative to the second portion of the optical signal propagating in said second arm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
a second resonator having a second refractive index and being operatively coupled to said other one of said first and second arms across a second gap; and
a second voltage source connected to said second resonator for providing a second drive voltage thereto having a polarity opposite of the drive voltage provided to said resonator, wherein changes in amplitude of the second drive voltage cause said second resonator refractive index to change;
said changes in said second resonator refractive index causing a phase-shift in the second portion of the optical signal propagating in said second arm that is approximately equal to the phase-shift in the first portion of the optical signal caused by said resonator coupled to said first arm.
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20. A low drive voltage optical modulator comprising:
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a Mach-Zehnder interferometer having an input waveguide, first and second arms connected to said input waveguide splitting an input optical signal having a predetermined wavelength into a first portion and a second portion, and an output waveguide connected to said first and second arms;
first and second resonators each having a refractive index and each being operatively coupled to a respective one of said first and said second arms across a respective gap; and
a voltage source connected to each of said first and said second resonators for providing a respective drive voltage of opposite polarity thereto, wherein changes in amplitude of the respective drive voltage cause said respective refractive index of said first and said second resonators to change;
said changes in said first resonator refractive index causing a first phase-shift in the first portion of the optical signal propagating in said first arm and said changes in said second resonator refractive index causing a second phase-shift in the second portion of the optical signal propagating in said second arm. - View Dependent Claims (21, 22, 23, 24)
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25. A low drive voltage optical resonator comprising:
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a Mach-Zehnder interferometer having an input waveguide, first and second arms connected to said input waveguide splitting an input optical signal having a predetermined wavelength into a first portion and a second portion, and an output waveguide connected to said first and second arms; and
a phase-shifter for causing a predetermined phase shift in the first portion of the optical signal propagating in said first arm and being operatively coupled thereto across a gap. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
a first resonator having a refractive index; and
a voltage source connected to said first resonator for providing a drive voltage thereto, wherein changes in amplitude of said first resonator drive voltage cause said first resonator refractive index to change, said changes in said first resonator refractive index causing a first phase-shift in the first portion of the optical signal propagating in said first arm.
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27. The optical modulator of claim 26, further comprising a second phase-shifter for causing a predetermined phase shift in the second portion of the optical signal propagating in said second arm and being operatively coupled thereto across a gap.
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28. The optical modulator of claim 27, wherein said second phase-shifter comprises:
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a second resonator having a refractive index; and
a voltage source connected to said second resonator for providing a drive voltage thereto, wherein changes in amplitude of said second resonator drive voltage cause said second resonator refractive index to change, said changes in said second resonator refractive index causing a second phase-shift in the second portion of the optical signal propagating in said second arm.
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29. The optical modulator of claim 25, wherein said Mach-Zehnder interferometer and said phase-shifter each comprise a relatively high refractive index photonic wire semiconductor waveguide having a core surrounded in all directions transverse to photon propagation direction in said interferometer and said phase-shifter by a relatively low refractive index medium and materials.
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30. The optical modulator of claim 25, wherein said Mach-Zehnder interferometer and said phase-shifter each comprise a relatively high refractive index photonic well semiconductor waveguide having a core surrounded on opposite sides in a direction transverse to photon propagation direction in said interferometer and said phase-shifter by a relatively low refractive index medium and materials.
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31. The optical modulator of claim 26, wherein the predetermined phase shift is between approximately 0°
- and π
° and
wherein said drive voltage is less than or equal to approximately 5 VAC.
- and π
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32. The optical modulator of claim 27, wherein the predetermined phase shift caused by each said phase-shifter is between approximately 0°
- and π
° and
wherein each said drive voltage is less than or equal to approximately 5 VAC.
- and π
Specification